With Built-in Micro USB cable, when you place the Samsung Galaxy S 4 IV i9500 charged battery into the space, and connect your phone to the port, then your phone is ready to charge, no other extra cables required

You can also charge your phone directly by connecting the another Micro USB cable(not included) powered by pc or wall plug(not included), but without the external battery placing in the space

Or charge your phone and spare battery simultaneously by linking the other Mirco USB cable(not included)